Locus heterogeneity

Locus heterogeneity exists when the same disease phenotype can be caused by mutations in different loci. Locus heterogeneity becomes especially important when genetic testing is performed by testing for mutations at specific loci. 

Locus heterogeneity for diseases that can be caused by mutations in two or more different genes... 

These two forms of muscular dystrophy are known to be encoded by the same locus, so locus heterogeneity (choice D) is excluded. 

Osteogenesis imperfecta is a good example of a disease in which locus heterogeneity (choice C) is observed, but this principle refers to the fact that a mutation in either the type 1 procollagen gene on chromosome 7 or the type 1 procoUagen gene on chromosome 17 can result in imperfect formation of the trimeric protein. This principle does not explain the co-occurrence of ftactures and blue sclerae. 

Linkage analysis can identify locus heterogeneity (see Chapter 1), which must be identified to perform an accurate genetic diagnosis (see Clinical Correlate). 

Locus heterogeneity refers to the condition when mutations of more than one gene or locus can produce similar disease states. 

Palmer, S.E., Scherer, S.W., Kukolich, M., Wijsman, E.M., Tsui, L.C., Stephens, K., Evans, J.P. 1994. Evidence for locus heterogeneity in human autosomal dominant split hand/split foot malformation. Am. J. Hum. Genet. 55, 21-26. 

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